Backsweetening and priming cider with Cherry Juice?

[Genacide]

I'm making 3 gallons of cider with a recipe very close to EdWort's Apfelwein, with the exception of using Lalvin EC-1118. What I would like to do is backsweeten and prime with Black Cherry juice and then stove top pasteurize after the bottles are carbed properly, but keep as much of the cherry sweetness and taste as possible. I'm almost 3 weeks in with the Apfelwein and have a couple questions.
When should I add the cherry and bottle it? How long will it take to carb? How much cherry juice should I add? Will this age well after bottleing and pasteurizing, or should all the aging be done in the secondary (or primary if I don't rack).

Thanks for any advice!

 

[dinnerstick]

i have done this, added fresh cherry juice to prime, with extra sugar as well for a fairly sweet drink, pasteurized. you can take a hydrometer reading on the cherry juice, if it's very sweet you might get away with just juice and no sugar to reach the sweetness you want, but since you are pasteurizing, just do it by taste. bear in mind black cherries are all sweet and no acidity, you might consider tart cherries and sugar? the biggest problem with my one batch is that the fresh cherry juice i used generated so much lees during the bottle conditioning, combined with maybe setting pectin or glomping together proteins / polysaccharides from the fresh juice when heated, there is a thick dark blob in the bottom of the bottles, which is fine but not convenient.
when should you add the juice? when your cider is done fermenting and clear to your satisfaction. if you are going for a sweet drink then you generally don't need to age, unless it's really boozy and you need it to mellow out. there is no answer for how long it will take to carb, too many variables at play, you have to determine this empirically batch by batch. i recommend bottling one in a plastic soda bottle so you can check by feel when it is in the right ballpark. as for the cherry flavor, it really worked in that regard, it is all cherry, but unfortunately (stupidly) i oversweetened so it is a bit cough mediciney. but cherry season is in full swing here so i'm going back to the orchard this weekend!!